A considerable amount of evidence, both molecular and serological, has been collected to infer that HHV-8 is the etiological agent associated with Kaposi's sarcoma and non-Hodgkin's lymphomas in acquired immunodeficiency disease syndrome (AIDS) patients. However, direct evidence for HHV-8 as the causative agent would require an appropriate animal model that closely parallels aspects of the disease in humans. We now report the isolation of a rhesus HHV-8 homologue from bone marrow of a simian immunodeficiency virus (SIV)-infected rhesus macaque with lymphoproliferative disease in lymphoid and nonlymphoid tissue. The virus induces cytopathic effects and the synthesis of herpesvirus particles in a primary rhesus cell culture. To define which class of herpesviruses this isolate is a member, we designed degenerate PCR primers to amplify a conserved region of the DNA polymerase gene from a and herpesviruses. Rhesus cytomegalovirus and rhesus Epstein-Barr virus were included as controls for other herpesviruses. The resulting PCR-generated fragments were cloned and the DNA sequence determined. Comparison of the deduced primary amino acid sequence of each sample revealed this isolate is a member of the 2 herpesviruses. Further evidence was provided by the isolation and DNA sequence analysis of fragments with close sequence similarity to the major capsid protein of HHV-8. With the use of immunomagnetic bead selection, we have isolated subsets from the PBMC and localized the virus to the CD20+ B cell population. These studies suggest that a suitable animal model for investigating the viral etiology of AIDS-related malignancies and how HHV-8 can potentially impact AIDS pathogenesis is available.